A typical concern with valve train lubrication in an internal combustion engine is assuring an adequate supply of oil on the cam lobes while the engine is operating, for all engine conditions. When the camshaft in an overhead cam engine, in particular, is operating, it is critical that the cam lobes are well lubricated. This is typically done using the engine oil. Without adequate oil supply to the cam lobes, the components can overheat and fail. Thus, the supply of oil to lubricate the lobes is critical under all operating conditions and engine speeds, including low engine speeds.
An example of one current method of supplying oil is to allow oil to bleed off out of top holes in lash adjusters through holes in roller finger followers. The oil then flows by the force of gravity along the top surface of the body of the roller finger follower toward the areas in need of lubrication. While this works adequately for some geometries of cam and roller configurations, oil does not always flow properly for all configurations.
Of particular difficulty with the geometry of overhead cam engines is when one of the two sets of valves is located above all but the valve contacting tip portion of the roller finger followers such that gravitational force will cause the oil to flow away from rather than toward the critical areas in need of lubrication. That is, the oil will flow off of the roller finger follower and down to the tappet gallery floor, thus providing no lubrication to the cam lobes and roller of the roller finger follower.
Some attempted solutions to this problem include adding extra oil passages around the cams to supply oil directly to the cam lobes, at the added cost, weight of additional parts and loss of oil pressure in the overall system; or adding parts that force oil to be sprayed onto the cams at the expense of additional parts and the resultant loss of oil pressure in the overall oil system. Thus, the need arises for an oiling mechanism that will assure adequate oil supply to the cam lobes at all engine speeds while not losing oil pressure or adding significant cost increases.